Technical Field
This document relates to a display device, and more particularly, to a display device with built-in touch sensors.
Discussion of the Related Art
In recent years, flat-panel displays (or display devices) with large size, low price, and high display quality (video representation, resolution, brightness, contrast ratio, color reproducibility, etc.) have been increasingly developed to meet the need for display devices capable of properly displaying multimedia content, along with multimedia development. For such flat-panel displays, various input devices, such as a keyboard, a mouse, a trackball, a joystick, a digitizer, etc., may be used to configure an interface between a user and a display device. However, using such input devices requires the user to learn how to use them, and also they take up space for installation and operation, making it difficult to increase the maturity of the products. In light of this situation, there is a growing demand for input devices for displays that are convenient, easy to use, and can reduce glitches. In response to this demand, a touch sensor has been introduced in which an input is detected when the user enters information while viewing the display device by directly touching the screen with their hand or a pen or moving it near the screen.
Touch sensors for use in display devices may be implemented as in-cell touch sensors that are embedded in a display panel. An in-cell touch display uses a method in which a touch sensor's touch electrode and the display panel's common electrode are used together. Here, driving is done in a time-sharing manner, separately in a display period and a touch sensing period. That is, the common electrode receives a common voltage during the display period and a touch drive signal during the touch sensing period.
Because the common electrode has a parasitic capacitance with a data line, data voltages applied to the data line during the display period cause the voltage applied to the common electrode to change due to capacitive coupling, thereby causing a ripple in the common electrode voltage. When there is a ripple in the common electrode voltage, especially at the end of the display period, it affects the voltage level of the touch drive signal in the initial part of the touch sensing period, thus generating touch noise.